The traditional card trading machine is divided into two types: online transactions credit card machine and off-line credit card machine, the online transactions credit card machine must be installed to a fixed position and can be connected to a network, likes the credit card swipe machine in the shops. The off-line credit card machine even is no need to be installed to a fixed position and connected to the network, but still need to swipe the card transactions and thereafter connected to the back-end systems, is the way after connection to complete the credit card verification jobs, because the offline online credit card machine can not verify the validity of the card, thus making the risk of receivables relative increased. The off-line credit card machine is such as the credit card machines on the airplanes. For the online transactions credit card machine and the off-line credit card machine, in addition to the above-mentioned drawbacks, the credit card machine purchase costs are also high.
Currently, some of the publication discloses some technical features to improve the traditional problem of credit card machines, increase the convenience of card transactions, and also reduce the cost of the credit card machine, for example, the U.S. Pat. No. 7,810,729 “Card reader device for a cell phone and method of use” disclose a small card reader device to be connected on the smart phone's audio holes, make the smart phone instantly turn into a mobile credit card machine, which can be completed immediately for the online credit card transactions, but also easy to carry. The technology of the card reader device is mainly configured to transfer the card transaction data into audio signals and then transmit the audio signal to the smart phone, thereafter the smart phone restores the audio signal to become the card transaction data, and finally the data will be uploaded to the bank's database. Even though the U.S. Pat. No. 7,810,729 “Card reader device for a cell phone and method of use” has solve the problems of the traditional credit card machine cannot be easy to carry and cannot immediately instant the online credit card transaction, but the card reader device still has the following disadvantages:                1. When the card reader device reads the data of the card and transfers it into audio signal, it's likely to cause a crash, resulting in failure of credit card transactions, and thus requiring the user to restart the device for the device working properly.        2. The card's transaction digital information has been encoded through conversion once, so the encoded data after conversion is easier to be cracked, and is lack of security.        
Therefore, how to design a card transaction device, to make the card transaction device in use effectively reduce the incidence of failure and increase the security of the transaction, is worthy to be considered by the person having ordinary skill in the art.